Treat SHOW DATABASE as an observer statement

**Describe the problem**

`SHOW DATABASE` is not recognized as an observer statement (see connExecutor.runObserverStatement [1]), leading to a clunky experience in the DB console, especially when viewing transactions that were executed via the cli shell `cockroach sql`.

The shell performs many intermediate statements with each statement input by the user. Specifically `SHOW SYNTAX`, `SHOW LAST QUERY STATISTICS`, `SHOW TRANSACTION STATUS` and finally `SHOW DATABASE`

All these get categorized as observer statements, and thus they don't get to the point in the conn executor where they get recorded to statement statistics (`connExecutor.recordStatementSummary` [2]), except for `SHOW DATABASE` leading to a confusing experience when viewing the transaction fingerprint (see screenshot)

**To Reproduce**

Open a SQL shell w/ `cockroach sql` and perform an explicit transaction with a few statements.
In this example, i did
```
BEGIN;
INSERT INTO foo VALUES (1);
SELECT * FROM foo;
COMMIT;
```

Go to SQL activity page in DB console > Transactions, click on your transaction, notice that there are intermediate `SHOW DATABASE` statements that are included in the transaction fingerprint.

**Expected behavior**
Expecting not to see `SHOW DATABASE`

**Environment:**
All versions of CRDB.

[1] https://github.com/cockroachdb/cockroach/blob/master/pkg/sql/conn_executor_exec.go#L3669-L3695
[2] https://github.com/cockroachdb/cockroach/blob/master/pkg/sql/executor_statement_metrics.go#L134-L144

Jira issue: CRDB-54770

Start in pkg/sql/conn_executor_exec.go at connExecutor.runObserverStatement and compare SHOW DATABASE with the other observer statements described in the issue. Check pkg/sql/executor_statement_metrics.go to understand the recording path; done means SHOW DATABASE is excluded from the transaction fingerprint like SHOW SYNTAX, SHOW LAST QUERY STATISTICS, and SHOW TRANSACTION STATUS.

Written by the indexing model from the issue text.